Evidence of 4-Cl-IAA and IAA bound to proteins in pea fruit and seeds

Seijin Park, Jocelyn A. Ozga, Jerry D. Cohen, Dennis M. Reinecke

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

The auxins 4-chloroindole-3-acetic acid (4-Cl-IAA) and indole-3-acetic acid (IAA) occur naturally in pea vegetative and fruit tissues (Pisum sativum L.). Previous work has shown that 4-Cl-IAA can substitute for the seeds in the stimulation of pea pericarp growth, whereas IAA is ineffective. Both auxins are found as free acids and as low-molecular-weight conjugates from organic solvent-soluble extracts from pea fruit. Here we present evidence for an additional conjugated auxin species that was not soluble in organic solvent and yielded 4-Cl-IAA and IAA after strong alkaline hydrolysis, suggestive of auxin attachment to pea seed and pericarp proteins. The solvent-insoluble conjugated 4-Cl-IAA in young pericarp was on average 15-fold greater than solvent-soluble 4-Cl-IAA. The solvent-insoluble conjugated IAA was approximately half the levels reported for the solvent-soluble IAA fraction. To identify putative 4-Cl-IAA-bound proteins, polyclonal antibodies were raised to 4-Cl-IAA linked to bovine serum albumin protein (BSA). Immunoblots probed with anti-4-Cl-IAA-BSA antiserum detected three to four unique bands (32-40 kDa) in primarily maternal tissues, and a different set of protein bands were detected in mainly embryonic tissues (ca. 65-74 kDa in mature seed). 4-Cl-IAA and IAA were also identified from protein fractions separated by polyacrylamide gel electrophoresis using GC-MS. These data show that the majority of 4-Cl-IAA, the growth-active auxin in young pea pericarp, and significant levels of IAA are linked to protein fractions. Auxin-proteins may function in regulation of free bioactive 4-Cl-IAA and IAA levels, and/or 4-Cl-IAA or IAA may be targeted to specific proteins post-translationally to modify protein function or stability.

Original languageEnglish (US)
Pages (from-to)184-193
Number of pages10
JournalJournal of Plant Growth Regulation
Volume29
Issue number2
DOIs
StatePublished - Jun 1 2010

Keywords

  • 4-Chloroindole-3-acetic acid
  • Auxin conjugation
  • Auxin-protein
  • Fragaria vesca
  • Fruit protein modification
  • Pisum sativum

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